Many commentators have argued that Donald Trump’s dominance in the GOP presidential race can be largely explained by ignorance; his candidacy, after all, is most popular among Republican voters without college degrees. Their expertise about current affairs is too fractured and full of holes to spot that only 9 percent of Trump’s statements are “true” or “mostly” true, according to PolitiFact, whereas 57 percent are “false” or “mostly false”—the remainder being “pants on fire” untruths. Trump himself has memorably declared: “I love the poorly educated.”

But as a psychologist who has studied human behavior—including voter behavior—for decades, I think there is something deeper going on. The problem isn’t that voters are too uninformed. It is that they don’t know just how uninformed they are.

Psychological research suggests that people, in general, suffer from what has become known as the Dunning-Kruger Effect. They have little insight about the cracks and holes in their expertise. In studies in my research lab, people with severe gaps in knowledge and expertise typically fail to recognize how little they know and how badly they perform. To sum it up, the knowledge and intelligence that are required to be good at a task are often the same qualities needed to recognize that one is not good at that task—and if one lacks such knowledge and intelligence, one remains ignorant that one is not good at that task. This includes political judgment.